


I Once Loved Sin Itself

by Exaggerated_Specificity



Category: Supernatural
Genre: Anal Sex, Barebacking, Bottom!Sam, Choking, Coming Untouched, Demon Blood Addiction, Demon Dean Winchester, Demon posession, Demon!Dean, Dubious Consent, Evil Dean Winchester, M/M, Oral Sex, Riding, Rough Oral Sex, Sam On Demon Blood, Season/Series 09, top!dean
Language: English
Status: Completed
Published: 2014-05-08
Updated: 2014-05-08
Packaged: 2018-01-24 00:17:37
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,890
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/1584701
Author URL: https://archiveofourown.org/users/Exaggerated_Specificity/pseuds/Exaggerated_Specificity
Summary: <blockquote class="userstuff">
              <p>Dean goes dark side and Sam can't bring himself to stop his brother.  He starts out as Dean's prisoner in the bunker but gets hooked on Dean's blood and Dean's dick.  The need inside Sam turns him quickly into his brother's willing consort.  Sam doesn't want Dean to stop until he takes him completely.</p><div class="center">
  <p>
    <br/>
    <img/>
  </p>
</div> <p>This was inspired by a conversation <a href="http://archiveofourown.org/users/dollylux/pseuds/dollylux">dollylux</a> and I had after watching the most recent Season 9 episode "King of the Damned."</p><p>The title is from a Timber Timbre song called 'Mercy'</p>
            </blockquote>





	I Once Loved Sin Itself

**Author's Note:**

  * For [dollylux](https://archiveofourown.org/users/dollylux/gifts).
  * Translation into 中文 available: [【授权翻译】I Once Loved Sin Itself |by：Exaggerated_Specificity](https://archiveofourown.org/works/1607933) by [whiyn](https://archiveofourown.org/users/whiyn/pseuds/whiyn)



The weeks following Dean going full dark-side were some of the worst in Sam’s memory. It was worse than countless days stuck in an endless loop of Dean dying at the hands of the cruel Trickster. Worse than watching his brother ripped to shreds and dragged into the pit by hell hounds. Worse than the year Sam wandered lost and aimless, believing Dean was dead. It was even worse than the lies, shame, and guilt that had piled up around them like soaring, wobbly pillars of misery, leaving Sam wishing for the sweet release of death. This was different. Dean was here, in front of him, alive. Dean was still what Sam ate, breathed, and slept every minute of every day. Only now, Dean was a demon, the enemy. And Sam was his prisoner.

Sam fought back at first. Well, as much as he could anyway. But despite Dean’s leatherette eyes and malicious sneer, Sam couldn’t bring himself to do what he knew deep down needed to be done. He’d even held the demon killing knife heavy in his palm, turning it, imagining the feel of it sinking into flesh and bone, working up the courage to strike. But when Sam pictured driving in into his own brother’s sternum, watching his body burn from the inside-out, like lava was seeping up from underneath his skin, Sam dropped their trusted weapon on the concrete floor of the bunker and fell to his knees, defeated.

The problem was that Dean was still Dean, even in this form. He wasn’t possessed, he had transformed. The Mark of Cain had just blackened, hardened, and twisted Dean, changing his soul into the distilled, hateful poison he always believed he was anyway. That made it complicated. Even after Dean imprisoned Sam in the bunker’s dungeon, even with all the bitterness and resentment that had built up between them over the years, Sam couldn’t – he _wouldn’t_ – kill Dean, even if he managed to figure out a way.

Sam wasn’t sure he’d ever have a chance, even if he found the resolve. Dean had taken precautions almost immediately, using his fledgling powers to pin Sam against the wall, putting him in manacles while Sam still had the desire to fight back. Dean was surprisingly gentle with Sam in those days, not nearly as cruel as Sam knew he could be. Dean had been one of Alistair’s best pupil’s after all and under the influence of the First Blade Sam had seen his brother do and say things that gave him chills. But Dean never turned those skills toward Sam and for that he was thankful.

He tried to appeal to Dean’s reason, talk his way out of the chains. But Dean didn’t feel like talking. Dean’s blood tasted like ambrosia on Sam’s lips the first time his brother ripped open the skin of his wrist and pressed it to Sam’s mouth as he fought desperately against the restraints. Sam tried not to groan with wanton bliss as the salty-dark nectar glazed his tongue and dripped down his throat, filling his mind with a delirious, sinister cloud. By the time Dean’s tongue was chasing his blue-black blood into the depths of Sam’s mouth, he was already rock-hard in his jeans and bucking his hips, desperate for friction that Dean was more than willing to give.

It didn’t take long for the metal shackles to come off after that first taste. Sam was bound now by restraints far more powerful than steel or iron. He was hooked on Dean’s blood and both brothers were surprised at how readily Sam’s body assimilated it and left him begging for more. The cocktail of Dean’s rich, earthy type-A, and the almost reverent touch of his lips, tongue, and fingers on Sam’s skin ensured he was going nowhere.

The power that surged in Sam, blossoming again under the wash of Dean’s blood, would have been a useful tool to the new King of the Damned. But Dean seemed less interested in ruling his demonic minions than making up for lost time. It made Sam’s anguish during those first few weeks after Dean turned almost worth it.

Now, Dean’s soft, sweet lips pressed against his forehead, rousing him from a warm, deep sleep.

“Rise and shine, baby boy.” Dean whispered, as gently as he could muster in his new form. The words dripped with lust and Sam could feel the heat and power of his brother’s body as it slid onto the bed next to his. Sam rubbed his hands over his face, pushing back his hair, smiling up at his gorgeous brother as his eyes fluttered open. He wasn’t sure he’d ever get used to the inky black depths of Dean’s new eyes. Sam reached up, tracing his fingertips over the sharp ridge of Dean’s cheekbone, thumbing the soft, crinkled skin at the corner of his eye.

“Mmmm, what is it?” Dean asks, turning his face into Sam’s hand, kissing the palm softly and nuzzling his lightly stubbled cheek into Sam’s slack fingers.

“Miss your pretty green eyes…” Sam says, too honest and soft from sleep for his own good. Dean could look normal if he wanted to, but he seemed to prefer his inky black stare, like it reminded him of how far he’d fallen. Sam knows it’s a touchy subject but his mouth feels loose and wet so he says it anyway, eyes pinned to Dean’s as his brother closes the space between them, bringing their mouths together. His expression is unreadable, but his lips show intent.

The kiss is deep, Dean’s tongue licking into Sam’s sleep-sour mouth hungrily, a soft growl emanating from his chest. Sam’s arms drape loose around Dean’s neck and he rotates his body to press against him, feeling the syrupy swirl of arousal churning in his stomach. Dean’s hands stroke Sam’s torso through the thin, tight cotton of his white v-neck t-shirt before sliding up underneath the hem. He traces lazy patterns into Sam’s abdomen with his fingertips, grazing over the skin with the edges of his fingernails. Goosebumps erupt in their wake and Sam’s nipples harden to stiff peaks under the almost translucent fabric.

“You want it, Sammy?” Dean breathes into the side of his neck as kisses turn to sharp but sweet bites and his hand slips down into Sam’s whisper soft sleep pants. His dick is already half hard, tenting the material, as Dean reaches in and strokes his cock gently. Sam groans, tossing his head, it still feels heavy on his neck from sleep and arousal.

“Tell me what you want.” Dean urges as his hot, wet mouth traps Sam’s right nipple through his t-shirt. He worries it between his lips and sweeps his broad, wet tongue over it, sopping the fabric with his spit. His thumbnail traces a tightening circle around the head of Sam’s cock, matching the motion of his tongue. There’s an electrified stream of pleasure flowing from his over-sensitive nipple to his thickening cock. Dean’s canines nip into the hard little bud in unison with his hand wrapping around the head, digging his thumbnail into the weeping slit.

“Dean, fuuuuck – ah…” are the only intelligible words in Sam’s litany of gasps and moans. The truth is Sam’s mind is on a single track, a deafening thump-thump-thump in his ears, one word, one need, repeated over and over: **_Dean_**. Words don’t matter, they’re not what Dean wants anyway. Dean feeds off of Sam’s needy desperation, his lusty hunger, just as much as Dean’s blood, sweat, and come are Sam’s addiction.

Sam’s body is a writhing sweaty mess after a few moments under Dean’s nimble fingers and tongue. Both nipples are sucked raw and red beneath the soaked, clingy cotton and his cock is leaking like a faucet where it strains, tip peeking out from under the elastic waistband of his pants, leaving a puddle of slick on his belly. Dean traces his fingers through it, dragging the precome up Sam’s happy trail, dipping into his exposed belly button. He pulls his finger away and sucks it between his plush lips.

Dean stands and pulls Sam’s PJ bottoms down. The rush of the soft fabric over the hair on Sam’s thighs makes his skin tingle with want. Sam claws up his own torso, hungry for the stimulation as he tugs his shirt up, wrestling with it a bit to get it off of his broad shoulders. Dean’s spit leaves a damp trail up the side of his face as he yanks it off, over his head.

Sam hears Dean undressing too and spreads his legs, pulling his knees up in a less than subtle invitation. He runs his hands over his pelvis and thighs, arching his back so his needy hole is on display for Dean who’s taking his sweet time getting back on the bed. He can already taste the coppery ghost of Dean’s blood on his tongue in anticipation. Sam imagines the thick crimson swirling with streaks of come, causing saliva to flood his mouth.

The harsh sound of the metal framed desk chair scraping across the concrete floor pulls Sam out of his fever dream.

“Gonna have to come over here to get what you need, Sammy.” Dean’s voice is low, tinged with his own desire.

Sam pulls himself up on one elbow to look down the foot of the bed at Dean. His hair falls over his forehead in a chestnut cascade, forcing his eyes to focus as he rakes it back. Dean’s seated, completely nude on the armless, high backed, metal chair. His back is straight and his hands rest on his knees like he’s sitting on a gilded throne. He’s staring, onyx-eyed, at Sam and he licks over his full, pink bottom lip. His cock stands proudly between his thighs, diamond hard with a shiny bead of precome welling up, glistening in his slit.

Sam has to swallow the spit flooding his mouth before climbing down the bed toward his brother. He feels like a man who’s been lost in the desert without food or water for a week. His throat burns dry and his salivary glands weep in desperation to taste Dean, everything he offers. Sam climbs like a jungle cat down the bed and mounts Dean’s lap, perching on his thighs, arms circling Dean’s neck, watching his face in wait.

“Kiss me…” Dean hums as Sam dips his head down. He wants to ravage that gorgeous mouth, bite at it until it’s raw and bleeding, sucking the blood from Dean’s torn lips, but he doesn’t. That’s not how things work between them. Instead, he licks slowly across Dean’s bottom lip, tasting his brother’s saliva, savoring it on his tongue like it’s a delicacy. Dean’s lips part and Sam licks in deeper, tongue sliding across Dean's smooth, ivory teeth. This is worship, this is a prayer. Sam has to make an offering to get what he wants. He wants flesh, he wants blood, but he wants more than anything to be filled, utterly and completely, and for that he must do penance.

Sam’s hands smooth over Dean’s tan, supple skin. He knows exactly where to touch and how to please Dean. He’s had a lot of practice. He kisses him slow and deep, just Dean likes it – lots of tongue, not too much spit. The tips of their erections bump as their mouths slide together indulgently. Sam tilts his hips forward and wraps his hand around their cock heads, curling his fingers around to create a dome. He thrusts gently, rutting his slick tip against Dean’s, applying pressure with his hand. Dean groans and tilts his head back, pulling away from the kiss. Sam gives their cocks a few more squeeze-strokes, raising his palm to lap at the clear, salty, slick coating his hand. His eyes slip closed involuntarily as his tongue drags through the mess.

“Suck me. Then you can have what you want…” Dean means he’ll nick his wrist with a blade and let Sam nurse at the wound like a hungry infant once Sam lets him fuck his throat. Sam wants it, wants it so bad he drops to his knees as if the floor is covered with a plush Persian rug instead of bare concrete, but Dean knows that isn’t what Sam needs. Not really.

Dean pulls Sam’s hair back into a loose ponytail in his fist as Sam takes his fat, dripping cock between his lips. He gathers the hair at the base of Sam’s skull, the perfect place to get the leverage to fuck several inches into Sam’s throat. He breathes through his nose and holds onto Dean’s firm thighs, willing his throat to open for the thick width of his cock. Maybe later Dean would flip him over on the bed and tilt his head back over the edge, lengthening his throat and letting Sam’s nose nestle in his ball sack as he fucked in much deeper than he could at this angle. Sam moans around Dean’s cock at the thought, the vibration eliciting a hungry growl from his brother.

“That’s right, open up. Fuckin’ choke on it, baby.” Dean was thrusting up and shoving Sam down simultaneously, making Sam gag as the blunt, thick head of Dean’s cock rammed into the back of his esophagus. He was drooling and his eyes watered but he took it, let Dean fuck into his face like it was an honor. It was. His need was that deep. Sam would take every indignity to feel whole again, if only for a fleeting moment. The only way he could be remade was like this, Dean buried as far as he could be into every one of Sam’s openings. He’d beg for it gladly.

There’s a sharp tug at the back of Sam’s head as Dean uses his hair to pull him off his dick. Sam gasps for air like he was held underwater for the past two minutes. Dean holds him up, cradling his head through the process, letting Sam’s breathing return to normal and watching as he wipes off his face, wet with tears and thick saliva. Dean’s dick was a pulsing, wet mess after being shoved halfway down Sam’s throat. Sam looked down at it with reverence.

“Get yourself ready for me.” Dean released Sam’s hair with the command. Sam slid three fingers into his swollen, fucked open mouth, wetting them generously with Dean watching. Sam turned and leaned over the foot of the bed, one foot on the floor and one up on the mattress. Sam ran his spit slicked fingers around his rim, already pliant and needy. He didn’t go more than twelve hours without something thick and heavy buried in his hole these days so it wasn’t like he needed much prep. Still, the lubrication was necessary and Sam twisted his digits, depositing his saliva in and around his asshole to help ease the way. He brought his fingers back to his lips a few times, sucking the bitter, earthy taste of his own ass off his hand to leave more saliva behind. He could feel Dean’s black eyes on him like there was actual heat emanating from his brother’s dark, hungry gaze. He fucked himself open, stretching and pulling, until his hole was wet, open and ready for Dean’s dripping cock.

Sam stood and turned, ready to mount Dean’s lap again, but instead Dean gripped his forearm, looking up into Sam’s face as he stopped him.

“No. Face that way.” Dean said voice low and harsh. Sam’s eyes slammed shut and he clenched his jaw as he turned back to face the bed. Penance indeed.

He sits back on Dean, back to front, legs spread, and holds onto Dean’s knee to balance himself, using the other hand to guide Dean’s cock to his entrance. From there it was only a matter of letting gravity take over. Sam arched his back, gripping his own trembling thighs, as he sank back onto Dean’s cock. The head popped past his rim with a gasp from both men and Sam let himself slide down the rest until his ass was settled against the curve of Dean’s pelvis.

“Mmmfuck… So fuckin’ deep this way. So good.” Dean groans, sounding almost blissful.

Sam’s muscles are starting to ache, it starts in his strained thighs as he begins to slide up and down on the thick pole buried in his ass. Sam knows the root cause is the deeper burn, his need for Dean’s blood. Sam tilts his head back, letting the soft curtain of hair tickle over his shoulders. He tips forward, hands planted on Dean’s knees and begins grinding up and down on his dick in slow, deep circles. He can hear his own moans growing high-pitched and needy, but he knew he wouldn’t be able to come when his body was thrumming with cravings.  
He’s minutely aware of movement behind him, the soft sound of metal on skin as Dean pulls a razor blade across the side of his wrist. Sam swears for a moment he can smell Dean’s blood, spicy-sweet against the musk of sex in the air. Dean wraps his left arm around Sam and pulls him against his body so his sweaty back is pressed tight against Dean’s chest. His dick slides in deep, all the way up into his guts so it feels like it’s going to bulge out of Sam’s stomach. It’s then Dean presses his bloody wrist to Sam’s lips.

Sam gasps as he sees the ruby-red sparkle moving toward his lips, almost in slow motion. He grabs Dean’s forearm greedily with both hands and latches on to the bleeding inch-long cut. Power surges through Sam as soon as the molten heat bursts salty and thick across his palette. He’d never tire of that feeling, especially when he was stuffed full of Dean’s cock while he experienced it.

“That’s a good boy. Keep riding that cock, baby. Fuck yourself on it while you drink your fill.” Dean growls against the sweaty plane of Sam’s back as he pinches and tugs one of Sam’s nipples. Sam can feel Dean's thick, rigid dick throbbing hot and deep inside him, in tune with the blood pulsing over tongue. Sam rocks his hips, trying to keep the same rhythm. He stays pressed against Dean, using his strong calves and thighs to piston his body up and down. Dean’s hands circle Sam’s hips and help him keep rhythm as he wavered back and forth between intoxication and the blissful heat blossoming from his hole. The curved underside of Dean’s cock was rutting against his swollen prostate and each thrust seemed to turn up the pressure building inside Sam’s body. Still, he couldn’t come. It felt like his orgasm was just outside of his grasp, even as he shoved himself down on Dean’s dick harder and harder.

Desperate, shaking, lips sticking to Dean’s already sealed up wound, Sam finally finds his voice. “Dean, please. Fuck, please, just a little bit. I need it, pleeeease… I can’t come. Can’t come unless you’re filling me upppp…” His words stutter out in hiccups, punctuated with gasps and grunts.

Dean knows what he’s asking for. He laughs gently, pleased with Sam’s breakdown, the desperation and helplessness in his words. The sound of his chuckle is raunchy, tainted – far removed from the bubbly barking laugh his bright-eyed brother used to possess. Sam gasps, so close and yet still so fucking empty it hurts.

“Okay, baby… shhhh… lemme give you what you need.” Dean bucks his hips a few times, making sure he’s seated deep inside Sam’s slick, fucked open ass. He pulls Sam against him, his head lolling back over his shoulder, long hair spilling over Dean’s face.  
“Here I come, baby.” Dean whispers as the thin wisps of smoke hiss from between his lips, curling in black tendrils around Sam’s neck and face, entering his mouth, filling his eyes with inky blackness.

The sensation is like nothing else in the world. It’s the blistering sensation of true completeness, like ascending to some other plain as a being of pure energy. Sam’s soul, finally made whole as the charred, smoky essence of Dean’s soul swirls around inside Sam's vessel, dancing and intertwining with his.

“Come for me…” Dean whispers, in his head, here beside him where Sam’s always needed him to be.

It’s an order he can’t disobey. His orgasm is the sting of a sharp blade splitting open a malignant ball of need seated in the pit of his loins. Every muscle in Sam’s body convulses and his balls empty, spurt after spurt of come erupting from his cock. Dean’s coming too, he can feel it, like a dark shadow billowing out around the sharp, bright light Sam’s own climax. He feels the hot surge of come injected deep into his belly, pulsing in time with his own cock unloading all over the floor. They are experiencing one another’s orgasms simultaneously. Sam would swear to all the angels and demons and God him-fucking-self that it rights all the wrongs in the universe, even if only for one brief moment.

He collapses against Dean as he feels his brother withdraw from his body. Dean’s essence departing Sam feels even more bittersweet than the slick, sucking sensation of Dean’s big dick slipping out of his fucked-out asshole. Sam gasps and tries to catch his breath, almost passing out from the shocking, soul-deep pain of being empty again, despite the heat of Dean’s demon blood surging in his veins.

Sam lets Dean stand him up to transfer him to the bed. He’s vaguely aware that he doesn’t even remember the last time he got up, took a shower, put on real clothes, or had a proper meal. It doesn’t matter, he’d stay fucked open and ready for his brother’s cock on the floor of the dungeon for the rest of his days if that’s what Dean wanted. Sam just blissfully buries his head into the musty pillow and lets his nerve endings sing with the power of the blood. Dean strokes his back for a while until his breathing returns to normal. He gets up then and brings back a wet, warm washcloth to wipe Sam off.

Sam takes his bath happily, glad for the intimacy and care from his demonic soulmate. He turns over and looks up at Dean as he swipes the cloth down Sam’s sweaty, come streaked abdomen. There’s the twinkle of green under the fan of Dean’s long lashes. Sam’s heart aches as his brother reveals the jeweled green orbs that he’s missed so much. They hold eye contact for a moment, tears welling up in Sam’s eyes, before Dean looks down, almost demurely, before flickering them back to his preferred shade of coal.

“Sammy, I –” Dean starts but Sam grabs his wrist and cups his hand over Dean’s cheek. Sam’s mind swirls with the crimson red and charcoal black of his brother’s soul but he swallows thickly and looks long and hard into the abyss of Dean’s stare.

“We’ll figure it out, Dean. We always do.” He swipes his thumb over Dean’s cheekbone again before slumping back into the mattress, limbs heavy, ready to sink back into his blood-addled haze. Dean kisses him softly and leaves Sam to rest, for now.


End file.
